The present invention relates in a general manner to radiology devices. More precisely, the invention relates to a device making it possible to obtain high-resolution digital images of e.g. objects, organs or tissues which one wishes to examine (which for the sake of simplicity will be referred to subsequently in this text by the generic term “subject”), as well as of any desired region of the subject.
The subject can be e.g. a living body. It can also be material for which detection and/or characterization is sought (this can be the case for application of the invention such as the detection of explosives in a vehicle, a container, . . . ).
Radiology devices which implement an X-ray source and a module making it possible to visualize the track of the X-rays having passed through the subject have been known and employed widely for many years. The following overall typology can be established for these devices:                radiography devices, in which the subject is interposed between an X-ray source and an X-ray sensitive film. This type of device which was historically the first to be used and which is the most widespread, thus provides static images of the subject which must remain immobile during exposure thereof to the X-rays for a time sufficient to obtain an impression of the film by the X-rays. This type of device has rendered great service; it nevertheless has drawbacks, the main ones of which are the following:                    limitation to the production of static images, thus precluding visualization of the dynamic evolution of the subject in order to characterize certain aspects of its functioning,            repeated exposure of radiologists to X-rays and health risk stemming therefrom,                        fluoroscopy devices on the other hand offer access to dynamic images. In these devices, the subject is interposed between an X-ray source and visualization means which in real time convert the X-radiation into a visible image. These means may thus offer:                    direct visualization. In this case, the radiologist directly visualizes the “primary” images which are the first images formed by the visualization means from the X-rays. The visualization means then consist of a converter of the phosphor coating screen type.            or indirect visualization. In this case, the device comprises means for acquiring the primary images at the output of a converter (the latter possibly being of the phosphor screen type), via a chain which may include a video camera filming the entire field of an output screen of the converter so as to form a “secondary” image, means for digitizing the image and means for processing, storing and distributing the images to various terminals (which may be on different sites).                        
In both cases (direct and indirect visualization), the visualization means allow dynamic viewing of the temporal evolution of the subject (visualization of the functioning of moving organs), thereby constituting an advantage and offering enhanced possibilities of implementation (recording of sequences illustrating the functioning of the subject, live operative assistance, etc.).
For medical applications, these fluoroscopy devices also have drawbacks however, among them being inferior image quality to that of radiography images (especially in terms of contrast), because of the necessary reduction in the intensity of X-ray emission for reasons of safety of the radiologist (and of the patients), the exposure to the radiation being lengthy.
To attempt to diminish the importance of this problem related to fluoroscopy devices, manufacturers have implemented intensifiers which make it possible to convert the X-radiation into an optical image with high efficiency (that is to say by producing a high number of photons per incident X-ray).
By increasing the intensity of the images produced and by thus improving their contrast and their sharpness, these devices make it possible to lower the intensity of the X-radiation to a level below that implemented in radioscopy; they can function in direct or indirect visualization mode. In both cases, the intensifiers comprise an output interface for displaying the primary images to an observer, or transmitting them to an image acquisition chain.
The fluoroscopy devices thus constitute an advantageous means of carrying out good-quality radiological examinations. It is moreover possible to carry out the examination of the subject according to two types of procedures:                based solely on images covering a single field containing the zone(s) of interest,        or else by taking successive snapshots of different zones of interest.        
The second type of procedure offers the advantage of greater flexibility of use, making it possible initially to take a wide-field snapshot so as to identify zones of interest, then to center the device successively on each of these zones.
For this type of use, especially in indirect fluoroscopy, image acquisition and enlargement means are generally provided for gathering the primary images as a whole, and then carrying out an enlargement of a part of the primary image centered on the desired zone.
However, this last type of use has the drawback of degrading the resolution of the secondary images which will be visualized, given that the secondary images which are enlarged have previously been discretized by the acquisition means: the resolution of the image observed is in this case N times lower than the resolution of the acquisition means, N being the enlargement coefficient.
Moreover, in the case of intensifier devices, the resolution of the primary image is already greatly limited by the resolution of the intensifier itself, which is commonly of the order of from 1 to 2 pairs of lines per millimeter only.
Such a drawback can result in the impossibility of detecting certain details of very small size, such as for example certain early symptoms of cancer of the stomach which are of millimeter size.
Furthermore, the intensifiers of fluoroscopy devices generally comprise curved input screens which produce aberrations in certain parts of the image.